What was found
FLT#391, BOS-TPA. 'VERY PRONOUNCED MUSTY, DIRTY SOCK SMELL NOTICED BY BOTH PILOTS IN THE FLIGHT DECK WHILE DESCENDING BETWEEN 14,000 AND 12,000 FEET. SMELL CAME FROM THE VENTS. TURNING OFF PACK 1 SEEMED TO CORRECT THE ISSUE. HOWEVER, THE AFT FLIGHT ATTENDANTS EXPERIENCED IT TOO. PACK 2 MAY BE CONTAMINATED AS WELL; COMPLIED WITH INFORMATION NOTICE 2017-T015, SECTION A, ISOLATED FAULT TO TYPE 10, (A), A, C PER TSM 05-50-00-810-085-B/ TSM 05-50-00-810-085-D. AIRCRAFT IS OK FOR SERVICE.'